How to Make It
In a large bowl, mix the chicken and pork with 1 tablespoon each of the olive oil and garlic and 1 teaspoon of the pimentón. Season generously with salt and pepper and mix again. Let stand at room temperature for 30 minutes.
Meanwhile, preheat the oven to 425°. In a small heatproof bowl, mix the saffron with the boiling water and let cool completely. Grate the tomato halves on the large holes of a box grater set in a bowl until only the skins remain; discard the skins.
In a 15-inch paella pan or large enameled cast-iron casserole, heat 2 tablespoons of the olive oil over high heat until shimmering. Add half the chicken-pork mixture and cook, stirring occasionally, until well browned but not cooked through, about 6 minutes. Transfer to a plate. Repeat with another 1 tablespoon of the olive oil and the remaining chicken-pork mixture.
Add the artichokes, romano beans, the remaining 1 tablespoon of olive oil and a generous pinch each of salt and pepper to the pan and cook, stirring occasionally, until lightly browned, about 3 minutes. Push the mixture to one side of the pan and reduce the heat to medium. Add the remaining 1 tablespoon of garlic and 1 teaspoon of pimentón to the other side of the pan and cook until fragrant, about 2 minutes. Add the grated tomatoes and the scallions and cook, stirring frequently, until the vegetable mixture is deeply colored and coated in a thick sauce, about 5 minutes. Stir in the chicken-pork mixture, 4 cups of the stock and the brewed saffron. Bring to a boil over high heat, then scatter the rice evenly on top, shaking the pan to distribute it evenly. Simmer over moderately high heat, shaking the pan occasionally, until slightly reduced, about 5 minutes. Add the rosemary sprig and the remaining 2 cups of stock and season with salt and pepper.
Transfer the paella to the oven and bake for about 15 minutes, until the rice is tender and the liquid is absorbed. Scatter the roasted red pepper and the peas on top and bake for 3 minutes more. Serve hot.